Generally, a gear wheel includes an outer side unit having a gear rim in a sawteeth shape outside, a hub having two opened sides and disposed coaxially to a center of the outer side unit, and a wall formed between the outer side unit and the hub or a connection unit having a connection bridge shape formed a radial direction.
Here, in order to form the connection unit, the opened sides of the hub are blocked, a flow hole is arranged at a top of a center of the hub, and then resin is injected in the radial direction to form the connection unit.
Then, after the connection unit is molded, resin adhered in an umbrella shape to the flow hole on top of a portion blocking the opened sides of the hub is cut, and a region where a side of the hub and the connection unit contact each other is processed to complete the gear wheel.
Such a gear wheel is disclosed in EP 1777439, and thus details thereof are omitted herein.
However, according to the gear wheel, since the resin is adhered in the umbrella shape to the flow hole while molding the connection unit, such resin needs to be removed separately after the connection unit is molded. Accordingly, a number of processes increases and thus a manufacturing time is increased.